1. Field of the Invention
The present invention relates generally to a process for producing a chromium containing molten iron which is suitable for use in production of stainless steel. More specifically, the invention relates to a process for producing a chromium containing molten iron from inexpensive material, such as stainless scrap and chromium (CR) ore or chromium containing oxide.
2. Description of the Background Art
It is generally and conventionally implemented technology for producing molten stainless mother melt, i.e. chromium containing molten iron for production of stainless steel, utilizing top-blown or top and bottom-blown converters for example. In production of such chromium containing molten iron, ferrochromium alloy, such as HCFeCR, has been used as source of chromium. The ferrochromium alloys are relatively expensive materials and cause high cost in production of the chromium containing molten iron. In view of the production cost, it is advantageous to use more inexpensive chromium oxide containing material, such as stainless scrap, chromium ore, semi-reduced chromium ore or pellets and so forth. In the conventional technologies, such replacement could not be realized because of low melting reduction efficiency.
In implementing production of chromium containing molten iron, the following problems have been left unsolved.
First of all, when stainless scrap is used as a source of chromium, heat absorption and lowering of carbon (C) concentration occurs to cause lowering of reduction efficiency of Cr oxide. Secondly, even when the amounts of carbon and oxygen are adjusted so as to establish heat balance in view of heat absorption, the reduction speed of Cr oxide is relatively low to cause expansion of the process period resulting in excessively high temperature of the molten iron. Excessively high temperature of molten iron causes acceleration of melting of the refractory.